KEYWORDS: Shadows, Radio propagation, Wave propagation, Waveguides, Transmitters, Receivers, Ionizing radiation, Analog to digital converters, Windows, Solar processes
The VLF signals from DHO and JXN registering in Yakutsk. During the solar eclipse on June 10, 2021 the maximum VLF amplitudes increased by 1.62 dB (11:39:18 UTC) and 1.4 dB (11:26:42 UTC) respectively. The relative changes of the ionizing radiation flux during an eclipse is characterized by the ratio of the areas of the open solar disk part to the total solar disk S(Φ)/S0. Along the DHO – Yakutsk and JXN – Yakutsk propagation paths the minimum average values S(Φ)/S0 are 0.532 (11:39:18 UTC) and 0.411 (11:33:00 UTC) respectively. The time of radio paths overlapping by the lunar shadow does not contradict the time interval of VLF amplitude variations registering in Yakutsk during the solar eclipse.
During the solar eclipse on June 10, 2021 for the JJY40 – Yakutsk radio path the amplitude signal changes were not registered, the phase delay decrease by 0.95 radians (11:14:06 UT) then the phase delay increase by 1.25 radians (12:02:24 UT). For the JJY40 - Tixie Bay path the amplitude increase by 5 dB (11:47:42 UT) and the phase delay increase by 1.2 radians (11:51:54 UT). The normalization coefficient was determined HJJY40-Tixie Bay = 4.93±0.54 km. The maximum change of the effective height of the Earth-ionosphere waveguide JJY40 – Tixie Bay for the maximum shading (11:39:18 UT) is 7.08 km (68° N, 132° E, Φ = 0.883).
Sudden phase anomalies of VLF signals (11.9 kHz) of RSDN-20 system (Novosibirsk, Krasnodar and Khabarovsk transmitters) registered in Yakutsk during 2009-2017 are considered. A catalog of X-ray solar flares from C3.0 class and higher is compiled for the period 2009 – 2017. Each flare is associated with the daily average value of the F10.7 index in solar flux units to characterize the background solar X-ray radiation. The array is divided into intervals corresponding to the minimum solar activity (SA): the F10.7 index is less than 122 sfu (quartile 25%), maximum SA: index F10.7 is greater than 160 sfu (75% quartile) and medium SA: 122 <F10.7 <160. In winter the SPA sensitivity to the intensity of the X-ray flux of solar flares is decreased from the solar activity (SA) minimum to the maximum one. There is an uneven distribution of the intensity of the background X-ray radiation from season to season. For the 24th solar cycle activity the main maxima of the F10.7 index and the maxima of the intensity of the solar background X-ray radiation fell on the winter seasons. By ground-based methods (based on data on the SPA of VLF radio signals and average daily values of F10.7) it is obtained satisfactory estimates of the intensity of the X-ray radiation flux during solar flares.
For the VLF propagation path NWC – Yakutsk the maximum increases of the signal phase delay were 0.652 and 0.48 radians for the annular solar eclipses of May 20, 2012 at 22:07:12 UT and December 26, 2019 at 06:07:30 UT respectively. Based on the solar eclipse circumstances and the Bessel elements the distributions of the eclipse linear phase and the ratio of open solar area to the full one along the propagation path NWC – Yakutsk are defined with a step 200 km and 126 seconds resolution for each distant element. The normalization coefficients relating the effective height changes of the Earth-ionosphere waveguide and the logarithm of the ratio of a solar radiation flux during the eclipse to a total radiation flux for the daytime are 2.597 ± 0.136 and 2.284 ± 0.178 km for the eclipses of May 20-21, 2012 and December 26, 2019 respectively. During the maximum shadowing of the NWC – Yakutsk radio path due to the solar eclipse of May 20, 2012 the maximum change of the effective height of the Earth-ionosphere waveguide is 4.71 km at 22:13:30 UT (for the segment 27° N 120° E, the eclipse linear phase is 0.953). For the eclipse of December 26, 2019, the maximum change of the effective height of the Earth-ionosphere waveguide is 4.29 km at 06:09:36 UT (for the segment 2° N 117° E, the eclipse linear phase is 0.962).
The maximum increase in the phase delay of the JXN radio signal during the solar eclipse on August 11, 2018 was 0.256 radians (09:48 UT) and 0.227 radians (09:56 UT) during VLF registration at Tixie Bay and Yakutsk, respectively. The normalization coefficients relating the effective height changes of the Earth-ionosphere waveguide and the logarithm of the ratio of the solar radiation flux during the eclipse to the total radiation flux for the daytime are 3.43 ± 0.21 and 2.23 ± 0.09 km for the JXN – Tixie Bay and JXN – Yakutsk radio paths respectively. According to our estimates for the segment of the JXN – Tixie Bay path (75° N, 113° E, a local maximum eclipse at 09:43:48 UT, the linear phase Φ = 0.628) the maximum increase of the effective height of the Earth-ionosphere waveguide was 2.28 km. For the segment of the JXN – Yakutsk path (70° N, 113° E, a local maximum eclipse at 09:56:24 UT, the linear phase Φ = 0.627) the maximum increase of the effective height of the Earth-ionosphere waveguide was 1.47 km. At the partial reflection radar of the PGI (69.0° N, 35.7° E) the eclipse was just before local noon when electron density of the lower ionosphere increased and the effect of a relatively weak solar eclipse was not detected (the maximum of the eclipse linear phase Φ = 0.313 at 09:27 UT).
A comparative analysis of seasonal variations in the parameters of the underlying surface under the conditions of the cryolithozone at the SHICRA SB RAS polygon near Yakutsk, far from industrial interference, was performed. Seasonal variations of the parameters of atmospheric electricity and the VLF radio waves propagation from 2009 to 2018 are presented. It was obtained that for the summer season the ground electric field has a recession due to summer defrosting of the upper layer of permafrost and changes in the conductivity of the underlying surface and an increase in permeability for radon output. In the seasonal variation of the VLF radio navigation signals received in Yakutsk in the summer season, there is also a slight decrease due to a forest cover conductivity changing.
KEYWORDS: Solar processes, Radio propagation, Signal attenuation, X-rays, Transmitters, Magnetism, Solar energy, Wave propagation, Signal detection, Solar radiation
Amplitude and phase variations of radio signals (11.9 kHz) of Khabarovsk and Krasnodar transmitters registered in Yakutsk and Tiksi during solar flares activity on September 04 – 10, 2017 are considered. The solar flares effects determined in a VLF signal phase delay during daytime propagation. The magnetic storm appeared on September 8 in amplitude and phase variations of VLF signals recorded in Yakutsk. The Khabarovsk signal amplitude decreased by 8 dB on September 8 (nighttime propagation). The phase delay of Krasnodar signal decreased by 70 degrees on September 8 (nighttime propagation) and by 40 degrees (daytime propagation) on September 9. For Khabarovsk – Tiksi propagation path the signal phase delay reduced by 35 degrees and the attenuation increased by 3.5 dB (19:40 UT) on September 10, 2017. For Krasnodar – Tiksi propagation path the signal phase delay decreased by 40 degrees (17-18 UT) on September 10, 2017. For Khabarovsk – Yakutsk VLF signal propagation path there is a phase delay decreasing by 6 degrees (daytime conditions: from 21 UT September 10 till 06UT September 11, 2017). According to the receiver in Yakutsk the phase delay of the Krasnodar signal decreased by 60 degrees on September 10 for a nighttime (17-18 UT) and the phase delay decreased by 50 degrees for daytime conditions on September 11. There is an attenuation increase of the Krasnodar signal on September 10 (from 17-18 UT). Such circumstances are caused by a sharp increase in the flux of high-energy solar protons on September 10-11.
Dynamics of seasonal variations in the amplitude of the VLF radio signal received in Yakutsk from the navigation station near Novosibirsk and the radiation intensity in the wavelength range from 835 to 853 nm, where the P-branches of the OH band (6-2) are located, is present. The radiation variations give information about mesopause region measured at the Maimaga station (130 km from Yakutsk). Observation period from 2009 to 2015 covers period with minimum and maximum solar activity (solar flux F10.7). In the seasonal dynamics of the VLF amplitude signals and the mesopause temperature are observed annual, semiannual and third-annual variations, increasing during nighttime for VLF signals. The mesopause temperature and the VLF signal increase with increasing solar flux F10.7 in winter.
The magnitude of sudden phase and amplitude anomalies (SPA and SAA) on the Novosibirsk-Yakutsk, KrasnodarYakutsk and Khabarovsk-Yakutsk VLF radio propagation paths during 2009-2016 as a function of the solar X-ray flux are considered. From the minimum (2009-2010) to the maximum (2014) in 11-year solar cycle activity (SA), the SPA sensitivity to a solar flare X-ray flux decreases in winter. For the signal Novosibirsk: the slope of the linear model is 11.9 (for 2009-2010) and 13.1 (for 2014), the initial offset is 74.7 (2009-2010) and 78.7 (2014). For the Khabarovsk signal: the slope is 9.9 (2009-2010) and 15.3 (2014), the offset is 71.1 (2009-2010) and 94.2 (2014). The decrease in SPA sensitivity is noted due to an increase of the ionizing background flux. The decrease sensitivity of Krasnodar signal SPA was not detected due to large phase fluctuations. There is an increase in the VLF amplitude with increasing X-ray radiation flux in winter. In the summer, the saturation of Novosibirsk signal sudden amplitude anomaly occurs for the solar flare ionization flux 10-5 W/m2 . In summer, the amplitude of the Khabarovsk signal with an excess of the solar flare ionization flux of 3×10-6 W/m2 becomes less than the background value.
The measurements of electric currents flowing through pipelines buried in permafrost during lightning discharge terminating to ground near pipelines in Yakutia are presented. In addition, there are measurement results of telluric current flowing through pipelines during geomagnetic storms. The influence of a direct current flowing through the metallic pipe on the “pipe-ground” potential variation in the piece of pipeline with length of 150 m and diameter of 110 mm.
During the solar eclipse of May 20 - 21, 2012 in Yakutsk VLF radio signal phase variations are recorded. The variations are 0.77 and 0.54 radians for JJY40 and NPM radio stations respectively. By the radio signals phase variations a normalization factor is determined. The normalization coefficients are 3,27 ± 0,08 and 2,27 ± 0,05 km for paths JJY40 - Yakutsk and NPM - Yakutsk respectively. The effective height of the Earth-ionosphere waveguide changing for the maximum shading the path JJY40 - Yakutsk (22:47 UT) is 4.63 km. For the path NPM - Yakutsk the effective height changes in maximum shading (23:52 UT) are 4.25 km.
KEYWORDS: Solar processes, Interference (communication), Signal attenuation, Radio propagation, Global Positioning System, Antennas, Atmospheric sciences, Electromagnetism, Navigation systems, Receivers
Diurnal variations of radio noise intensity (14.88 kHz) registered in Yakutsk in June 2009-2014 is 10 dB, March - 9 dB, September - 8.7 dB, December - 7.3 dB. Diurnal variations of intensity of radio station VLF signals, radio noise intensity and the number of lightning discharges in Yakutsk are compared. VLF noise variations in summer 5-10 UT defined local thunderstorm activity. The period 11-20 UT for receiving radio noise defined distant thunderstorm cells in Western Siberia, the territory between Hinggan, Buretsky and Stanovoy mountaines. Radio signals from these areas propagate in similar paths like signals Novosibirsk and Khabarovsk navaid stations. The attenuation variations from a solar activity minimum to the maximum are estimated. Taking into account the changes of propagation attenuation of 1.2 dB (signal Khabarovsk) from a minimum to a maximum of solar activity in July, the power of VLF radio noise at a minimum on 7.6 dB greater than at solar activity maximum.
KEYWORDS: X-rays, Solar radiation models, Radio propagation, Data modeling, Solar processes, Satellites, Wave propagation, Waveguides, Transmitters, Receivers
Phase variations and sudden phase anomalies (SPA) VLF signals registered in Yakutsk from Novosibirsk radio station (14.9 kHz) for summer and winter daytime propagation conditions are considered. The threshold SPA sensitivity by Xrays flux P depends on the season weakly. SPA magnitude at fixed solar zenith angle X and X-ray flux P from summer to winter on the Novosibirsk – Yakutsk path is increased, SPA dependence on averaged along the propagation path of the cosine solar zenith angle is sharper in summer. X-ray flux is estimated according to the phase variations of the Novosibirsk radio signals. A satisfactory agreement with the simulated flux data from the satellite has been obtained booth in SPA, and unperturbed daytime conditions.
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